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Paser (Aminosalicylic Acid) - Drug Interactions, Contraindications, Overdosage, etc



(4) Drug Interactions:

Aminosalicylic acid at a dosage of 12 grams in a rapidly available form has been reported to produce a 20 percent reduction in the acetylation of isoniazid, especially in patients who are rapid acetylators; INH serum levels, half lives and excretions in fast acetylators still remain half of the levels seen in slow acetylators with or without p-aminosalicylic acid. The effect is dose related and, while it has not been studied with the current delayed release preparation, the lower serum levels with this preparation will result in a reduced effect on the acetylation of INH.

Aminosalicylic acid has previously been reported to block the absorption of rifampin. A subsequent report has shown that this blockade was due to an excipient not included in PASER granules. Oral administration of a solution containing both aminosalicylic acid and rifampin showed full absorption of each product.

As a result of competition, Vitamin B12 absorption has been reduced 55% by 5 grams of aminosalicylic acid with clinically significant erythrocyte abnormalities developing after depletion; patients on therapy of more than one month should be considered for maintenance B12.

A malabsorption syndrome can develop in patients on aminosalicylic acid but is usually not complete. The complete syndrome includes steatorrhea, an abnormal small bowel pattern on x-ray, villus atrophy, depressed cholesterol, reduced D-xylose and iron absorption. Triglyceride absorption always is normal.

In one literature report 8 hours after the last dosage of aminosalicylic acid at 2 gm qid serum digoxin levels were reduced 40% in two of ten patients but not changed in the remaining eight.


Overdosage has not been reported.


Hypersensitivity to any component of this medication.

Severe renal disease.

Patients with severe renal disease will accumulate aminosalicylic acid and its acetyl metabolite but will continue to acetylate, thus leading exclusively to the inactive acetylated form; deacetylation, if any, is not significant.

The half life of free aminosalicylic acid in renal disease is 30.8 minutes in comparison to 26.4 minutes in normal volunteers. but the half life of the inactive metabolite is 309 minutes in uremic patients in comparison to 51 minutes in normal volunteers. Although aminosalicylic acid passes dialysis membranes, the frequency of dialysis usually is not comparable to the half-life of 50 minutes for the free acid. Patients with end stage renal disease should not receive aminosalicylic acid.

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